This invention relates to a broach sharpening machine.
Broaches are tools which are normally of considerable length and comprise a plurality of teeth which when brought into contact in succession with a surface to be machined, give it a required finish and shape by each removing a determined chip thickness which normally varies from one tooth to another and depends on the increase in height of each tooth relative to the preceding tooth. In addition, the fact that the chip thickness removed varies from tooth to tooth means that normally the distribution pitch of the teeth also varies along the broach. Finally, the tooth profile can vary along the broach according to the surface shape to be obtained.
In this respect, it should be noted that broaches are extremely specialised tools, the use of which is justified only for mass production, and provided the broaches can be sharpened a certain number of times.
In general, a broach is sharpened, or rather the cutting edges of its teeth are reconditioned, by sharpening machines of the grinding wheel type, in which a grinding wheel head is moved manually in such a manner as to sharpen the broach teeth one after another. For this purpose, the operator has to identify the position of the cutting edge of each tooth visually, then remove the same chip thickness from each tooth while controlling the grinding wheel such that its outer periphery does not touch the base of the cavity between each pair of adjacent teeth.
Normally, the visual identification of the cutting edge of the teeth with respect to the grinding wheel leads to errors which automatically result in variations in the geometrical form of the broach.